1. Field of the Invention
The present invention relates to an improvement of a flat panel display device, particularly to the latest improvement for large scale integration of the display device combining onto an integrated circuit active elements for driving a corresponding a picture element, the picture element and the display medium.
2. Description of the Prior Arts
Recently, proposed is a display unit having a structure such that an integrated drive circuit is combined with the flat panel type matrix display device which utilizes electroluminescence (EL) or liquid crystal. The drive circuit comprises active elements corresponding to the picture elements integrated onto a silicon wafer, thus controlling partially and selectively the optical functions of display mediums layered on the upper side of said silicon wafer. In addition, from the point of view of forming a display unit which is as wide as possible, an attempt has been made to integrate active elements corresponding to said picture elements utilizing the SOS (Silicon On Sapphire) technique or the thin film transistor (TFT) technique in place of the silicon wafer. One of such solid state flat panel displays is explained, for example, in the U.S. Pat. No. 3,866,209 entitled "CHARGE-TRANSFER DISPLAY SYSTEM" by P. K. Weimer. In addition, flat panel display using the TFT technique is proposed, for example, in the paper by F. C. Luo et al. entitled "Design and Fabrication of Large-Area Thin-Film Transistor Matrix Circuits for Flat-Display Panels" introduced in the IEEE Transactions, Vol. ED-27, No. 1, January 1980, pp 223-230.
However, it is very difficult to realize a large size flat panel matrix display device combining active elements as explained above with the existing techniques. Namely, in the case of the structure which integrates active elements corresponding to picture elements using the silicon wafer, the size of the display screen is limited by to the size of the wafer, and moreover, it is considerably difficult from the point of view of yield to form active elements and light emitting areas of as many as 240.times.240 without any fault on the ordinary 3-inch wafer. Further, it is also difficult to form the active elements for driving and the light emitting areas in such a number corresponding to the required picture elements with satisfactory yield even when the SOS structure or the TFT structure is employed, and after all it is the largest object for the display device of this type to economically obtain a large size display screen.